Plz Help Me Out

I am new to java and am doing some modification on a web page.In one of the web page i have to create 3 listboxes nd populate them with data from database.In one of the listbox i have to select multiple items and correspondigly the other listbox should be populated.My problem is that when i am making multiple selection only some of the data is coming and also there is gap between the data.Here is the code
<HTML>
<HEAD>
<TITLE>Case Study Portal</TITLE>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<link rel="stylesheet" type="text/css" href="./casestudy.css" title="Default" />
<script LANGUAGE="Javascript" SRC="./calender.js"></script>
<script LANGUAGE="Javascript" SRC="./Validate.js"></script>